Monosodium titanate (MST) is an inorganic sorbent that effectively removes strontium, plutonium, neptunium, and other actinide trace elements from alkaline high-level waste solutions. MST also strongly adsorbs or ion exchanges with a number of metallic species in a variety of aqueous media. As an example of some of the prior uses of MST, reference is made to U.S. Pat. No. 6,268,307 entitled “Titania Bound Sodium Titanate Ion Exchanger” which issued on Jul. 31, 2001 to DeFilippi et al. and to U.S. Pat. No. 6,517,788 entitled “Method and Device for Separating Caesium, Strontium and Transuranium Elements Contained in Sodium Waste” which issued on Feb. 11, 2003 to Debreuille et al. In addition, more recent work with MST is reported in a paper entitled “Engineering Monosodium Titanate for Adsorption Column Processes” by C. A. Nash et al. in the WM '05 Conference of Feb. 27, 2005.
MST prepared for the treatment of strongly alkaline nuclear waste solutions features a spherically-shaped particle morphology with particles ranging in diameter from about 0.5 μm to 10 μm. This material has been found to readily adsorb other metal ions such as Au (III), (Cd (II), and Hg (II) at biologically relevant pH conditions. These biologically relevant pH conditions are in contrast to conditions (pH>>12) encountered when using MST to treat nuclear waste solutions produced from reprocessing of irradiated nuclear fuel and target materials.
Recently, a related family of amorphous titanate materials referred to as amorphous peroxotitanates (APT) have been found to be even more effective than MST for the separation of strontium and actinides from waste solutions. This discovery is reported in the following papers: “Development of Improved Sorbents for Radiochemical Separations at the Savannah River Site” by Hobbs, D. T.; Nyman, M. D.; Tripathi, A.; Medvedev, D.; and Clearfield, A. in the Proceedings of the Waste Management Conference, Tuscon, Ariz., Feb. 27-Mar. 3, 2005; “Development of an Improved Sodium Titanate for the Pretreatment of Nuclear Waste at the Savannah River Site” by Hobbs, D. T.; Nyman, M. D.; Poirier, M. R.; Barnes, M. J.; Stallings, M. E. in the Proceedings of the Symposium on Waste Management, Tuscon, Ariz., Feb. 26-Mar. 2, 2006; and, “A Family of Peroxotitanate Materials Tailored for Optimal Strontium and Actinide Sorption,” by Nyman, M. D.; Hobbs, D. T. in the Chemistry of Materials, published on Web Nov. 18, 2006.
While the prior art use of sodium titanates as mentioned above has focused generally on the separation of radionuclides in spent nuclear fuel, the affinity of the sodium titanates to adsorb or ion exchange with other metals has not been significantly investigated or developed. Accordingly, it is one object of the present invention to develop unique and novel processes and products that advantageously use the metal binding properties of sodium titanates at physiologically acceptable pH levels.
A number of metals are used as therapeutic agents in the treatment of diseases. These metals are often introduced as metal complexes in which metal ions are attached to organic ligands. The organic ligands are utilized to increase the solubility of the metals at physiological pH levels (ca. 7.3) which facilitates transport in the blood system for delivery of the metal to the affected organ. These ligands also reduce the systemic toxicity of the uncompleted metal ions. Often, large quantities of the metal complexes are injected systemically to provide sufficient amounts of metal for the desired therapeutic effect at a specific site. Systemic administration can be problematic and result in toxic reactions if metal ions accumulate and undesirable metal ion concentrations occur. Accumulated metal ions can prove difficult to remove from the affected organ or site due to low solubility at the physiological pH level and formation of complexes in tissues.
Accordingly, it is the object of the present invention to provide a novel method for metal ion delivery or removal using an inert inorganic substance such as monosodium titanate (MST) or amorphous peroxotitanates (APT) that are effective at the physiological pH levels. Novel uses of MST and APT are described below.